This invention relates to a high volume covered hopper car which more effectively utilizes the space over the trucks at the ends of the car, and which eliminates hatches, walkways, and the like from the roof of the car, thus permitting the car to fully utilize its height for lading volume, and yet fit within AAR clearances.
Covered hopper cars are typically used to transport particulate, granular, or pulverant ladings, such as flour, cement, plastic pellets or powders, and the like. Such covered hopper cars are shown in the prior co-assigned U.S. Pat. Nos. 3,339,499 and 3,490,387. Certain particulate ladings, such as plastic pellets or powders, have bulk densities such that the lading capability of a covered hopper car is limited by its lading volume capability rather than by the weight of the lading. Thus, there has been a long-standing need in the design of covered hopper cars to achieve as high a lading carrying volume as possible.
All railroad cars must fit within a three-dimensional clearance envelope, as defined by the Association of American Railroads (AAR). Generally, this AAR clearance envelope defines the maximum height, width, and length of a car such that the car will be able to negotiate railroad tracks across the country, and be able to pass through tunnels, over bridges, around curves, and past other trackside objects without interference. These clearance standards are specified in the AAR's "Specifications For Design, Fabrication, And Construction Of Freight Cars", which is in part set out in ACF Industries' Shippers' Car Line Division Service Bulletin 12a, entitled "Plate B and Plate C Clearance Diagrams", issued October, 1967, a copy of which is included in the file of the present specification, and is herein incorporated by reference.
Generally, two clearance diagrams or envelopes, known as AAR Plate B and Plate C are utilized. These clearance diagrams are actually composites of the clearance diagrams for all of the railroads in the country and may be considered to be a three-dimensional "tunnel" through which a car must be able to pass without touching the "tunnel". Not only must the car be able to pass through the "tunnel", but all car appurtenances, such as walkways, ladders, hatches, railings, etc., must also be kept within the limits of the diagrams. The AAR has defined a "base" car for both Plate B and Plate C clearances. In general terms, Plate B cars have a somewhat lower height (15 feet, 1 inch) than Plate C cars (15 feet, 6 inches), and may operate in unrestricted interchange service. Since Plate C cars are somewhat taller, these cars may operate in limited or restricted interchange service, and may be permitted only on certain routes. However, the restrictions placed on Plate C cars are relatively few in number, and for purposes of this disclosure, Plate C will be utilized as the standard clearance envelope for the railroad car of the present invention.
As will be appreciated, a freight car must not only be sufficiently narrow and less than a maximum predetermined height to pass through the AAR Plate C clearance diagram, but the maximum allowable width of the car is dependent on the distance between the centerlines of the trucks at the opposite ends of the car, and also on the amount of overhang or swing-out at the ends of the car. As will be appreciated, as a railroad car negotiates a curve, the center section of the car will move radially inwardly and the ends of the cars will move radially outwardly relative to a chord defined by the centerlines of the trucks of the car. The maximum curve considered by the AAR clearance diagrams is a 13 degree curve, having a radius of 441 feet, 8.375 inches. The AAR Plate C base car, having truck centers less than 46 feet, 3 inches, may have a maximum width of 10 feet, 8 inches. However, a car having truck centers spaced at the maximum permitted distance between truck centers of 81 feet, such a car may only be 8 feet, 2 inches wide. Cars of an intermediate length may have a maximum width between these two extremes, with the maximum width being dependent on the length of the car, as defined by the above-noted AAR specifications.
As disclosed in the co-assigned U.S. Pat. No. 4,598,646, a high volume covered hopper car, such as generally shown in the above-noted co-assigned U.S. Pat. No. 3,339,499, is disclosed in which the side sheets forming the sides of the hopper car body are made from three different radii of curvature thereby to both maximize the lading volume of the car and also so as to provide increased resistance to diagonal buckling. However, this last-noted high volume covered hopper car still utilizes hatches (or other openings) in its roof for loading purposes, and also utilizes sloped end sheets above the trucks of the car so as to provide for the gravity feed of the pulverant lading within the end hoppers of the car downwardly toward pneumatic outlets located inwardly of the trucks toward the center of the car and below the level of the trucks. Thus, the roof of such a high volume covered hopper car must be kept below the maximum height permitted by AAR clearance diagrams so as to provide space for hatches, manways, walkways, and the like. Additionally, a substantial amount of lading volume over the trucks of the car at each end thereof was lost, due to the sloped end sheets.
Nevertheless, the high volume covered hopper car disclosed in the above-noted U.S. Pat. No. 4,598,646, represented a significant advance in the covered hopper car art in that the lading volume of that car was approximately 6,404 cubic feet, which represented a 12.4 percent increase in lading volume over other so-called high volume covered hopper cars, while the weight of this new high volume covered hopper car and the efficiency with which it utilized materials from which the car was constructed compared favorably with other covered hopper car constructions which were thought to efficiently use their construction materials.
However, a need nevertheless exists for a covered hopper car which had even greater lading volume.
Also, prior art covered hopper cars typically were unloaded by means of pneumatic unloading systems, such as are described in the co-assigned U.S. Pat. Nos. 4,114,785 and 4,382,725. Generally, these pneumatic outlets extended transversely of the car, with one outlet being provided for each hopper compartment within the car. These prior pneumatic outlets conventionally included a control valve which may be selectively moved from a closed position in which the discharge of the lading from within the hopper is prevented, to an open position in which communication between a fluid conduit and the lading within the car is opened. Typically, in a pneumatic unloading outlet, the flow of air through the conduit causes the particulate lading discharged into the conduit via the control valve to be entrained in the flow of fluid (e.g., air) flowing through the conduit for being pneumatically conveyed from the car. Additionally, pneumatic outlets which incorporated air permeable sides were known which "fluidized" the lading so as to facilitate pneumatic unloading. However, these prior pneumatic outlets required considerable time on the part of attendants to connect pneumatic outlet lines to the pneumatic outlet nozzle, and to continually regulate the opening of the pneumatic outlet control valve so as to best facilitate unloading of the lading.
Heretofore, sloped end sheets were required in covered hopper cars so as to ensure gravity unloading of the lading in the end hopper toward the pneumatic outlet located below the level of the truck toward the center of the car. Thus, heretofore, it has not been practical to eliminate end slope sheets, and thus the space above the truck has not been utilized for lading volume.